The present invention relates, in general, to ultrasonic surgical blades for use in surgical instruments and, more particularly, to an ultrasonic surgical blade with improved cutting and coagulation features.
Ultrasonic instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic instruments, and particularly solid core ultrasonic instruments, are advantageous because they may be used to cut and/or coagulate organic tissue using energy in the form of mechanical vibrations transmitted to a surgical end-effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels and using a suitable end-effector, may be used to cut, dissect, or cauterize tissue. Ultrasonic instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer, through the waveguide, to the surgical end-effector. Such instruments may be used for open procedures or minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end-effector is passed through a trocar to reach the surgical site.
Activating the end-effector (e.g. cutting blade) of such instruments at ultrasonic frequencies induces longitudinal vibratory movement that generates localized heat within adjacent tissue, facilitating both cutting and coagulation. Because of the nature of ultrasonic instruments, a particular ultrasonically actuated end-effector may be designed to perform numerous functions, including, for example, cutting and coagulation. The structural stress induced in such end-effectors by vibrating the blade at ultrasonic frequencies may have a number of undesirable effects. Such undesirable effects may include, for example, transverse motion in the instrument waveguide that may lead to, for example, excess heat generation in the waveguide or premature stress failure.
Long thin ultrasonic waveguides, such as those used in instruments for minimally invasive surgery, are particularly susceptible to transverse vibrations introduced by imbalances in the end-effector. For certain applications, it is desirable to include one or more axially asymmetrical features, (e.g. blade curvature) to enhance performance of the end-effector. It may also be desirable to design such end-effectors to be relatively long, in order to facilitate certain surgical procedures. A method of balancing asymmetric ultrasonic surgical blades is described in U.S. patent application Ser. No. 09/106,661 filed Jun. 29, 1999, hereby incorporated herein by reference.
Although ultrasonic surgical instruments such as those described in U.S. patent application Ser. No. 09/106,661 have been eminently successful, some areas of improvement still remain. One complaint sometimes heard from surgeons is that cutting is too slow, or that control is not as precise as would be desired. Ultrasonic surgical blade edges are often dulled or rounded to slow the cutting process, thereby providing more heat delivery to the tissue during cutting. This improves hemostasis during cutting. It would, therefore, be desirable to design an improved ultrasonic surgical blade. It would further be advantageous to provide an ultrasonic surgical blade that cuts faster, while maintaining hemostasis desired by the surgeon. It would also be advantageous to provide an ultrasonic surgical blade that is more controllable and precise, to providing cutting where needed with significant control. An ultrasonic surgical instrument is described with improved cutting and coagulation features to provide these advantages and overcome the disadvantages of previous instruments.
The present invention is directed to an ultrasonic surgical blade including a top surface, a bottom surface and at least one cutting-edge. The cutting-edge is defined by a cutting-surface intermediate the top surface and the bottom surface, and whereby the top surface has a width greater than the width of the bottom surface. The cutting-edge is optimized to increase cutting speed of the blade while providing desirable hemostasis. Further, the blade may be straight or curved. In one embodiment, at least a portion of the cutting-surface is substantially parallel to at least a portion of the top surface. In still a further embodiment, the cutting edge is defined by a second cutting surface that intersects the first cutting surface to form the cutting edge. In yet another embodiment of the invention, the bottom surface further includes a first side-wall that intersects the first cutting-surface to form the first cutting-edge. Depending on the angle between the cutting-surfaces and the top surface, the cutting-edge may be sharp or blunt. In yet another embodiment of the present invention, a central ridge is provided on the bottom surface of the blade to eliminate blade burrowing and improve precision during coagulation. A second cutting edge may be formed by including a second intermediate cutting surface formed between the top and bottom surfaces. The second cutting edge may be further defined by a second cutting surface intersecting the second intermediate cutting surface and/or a second side wall intersecting the second intermediate cutting surface to form the second cutting edge.